A power distribution method and power distribution device for automatically compensating for reactive power

Abstract

The application discloses a power distribution method and power distribution equipment for automatic compensation of reactive power, and belongs to the technical field of reactive power compensation of electric power systems. The method generates target compensation quantities of reactive power of each phase by collecting current and voltage signals of three-phase lines, updates capacity values of compensation units through a capacity coefficient, generates multiple sets of compensation unit combinations in combination with the target compensation quantities and the capacity values, and extracts a target compensation unit combination from the multiple sets of compensation unit combinations based on a safety coefficient. Further, the capacity coefficient is corrected by calculating voltage fluctuation rates and compensation efficiencies after compensation, and the safety coefficient is updated by collecting working parameters of each compensation unit. The application can effectively improve the reliability of the compensation units by predicting capacity changes of the compensation units, and further improve the accuracy of reactive power compensation of three-phase lines.

Description

Technical Field

[0001] This invention relates to the field of reactive power compensation technology in power systems, and in particular to a power distribution method and equipment for automatic reactive power compensation. Background Technology

[0002] In hydropower engineering, inductive loads (such as motors and transformers) exhibit poor operational stability. Their operation leads to a decrease in the power factor of the power grid, resulting in significant reactive power loss. To improve grid efficiency and ensure voltage stability, reactive power compensation devices are typically installed on the user side or at distribution nodes. As described in Chinese Patent Publication No. CN1808826B, existing technologies typically employ dynamic compensation devices such as Static Var Compensators (SVCs), Thyristor Switched Capacitors (TSCs), and Thyristor Controlled Reactors (TCRs). These devices can automatically track and compensate based on the system's reactive power requirements. However, in practical applications, under conditions of severe load fluctuations or high harmonic content, three-phase imbalance and harmonic interference are prone to recurring problems in the power grid, leading to prolonged switching of capacitor compensation units. In actual engineering projects, prolonged switching of capacitor compensation units can easily cause their reactive power compensation capacity to drift. Furthermore, for similar reactive power, multi-stage capacitor switching systems often use the same combination of compensation units, resulting in repeated switching of some capacitor compensation units, affecting the overall service life and reliability of the device. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a power distribution method and equipment for automatic reactive power compensation. This invention achieves independent compensation for each phase through compensation units connected to the neutral line. A safety factor characterizes the repeated switching of the compensation units, and a capacity factor characterizes the capacity changes of the compensation units, making it more suitable for long-term switching environments in engineering practice. Furthermore, this invention corrects the capacity factor by predicting single-phase-to-ground voltage fluctuations through the neutral line, enabling more accurate prediction of capacity changes in the compensation units.

[0004] The technical solution of this invention is implemented as follows:

[0005] A power distribution method for automatic reactive power compensation includes the following steps:

[0006] Step 1: The distribution network is connected to multiple inductive loads via three-phase lines. Multiple compensation units with different capacities are configured between each phase sequence and the neutral line of the three-phase lines. The safety factor and capacity factor of each compensation unit are preset.

[0007] Step 2: Collect the current and voltage signals of the three-phase line on the load side, extract the fundamental components of the current and voltage, and calculate the current power factor and target compensation amount of each phase.

[0008] Step 3: Update the capacity value of the compensation unit based on the capacity coefficient, generate multiple sets of compensation unit combinations corresponding to the phase sequence by combining the capacity value and the target compensation amount of each phase, extract the target compensation unit combination from the compensation unit combination based on the safety factor, and calculate the target compensation current;

[0009] Step 4: Activate the target compensation unit combination. After the system stabilizes, re-acquire the current and voltage signals of the three-phase lines, and calculate the actual compensation current of each phase and the voltage fluctuation relative to the neutral line.

[0010] Step 5: Update the capacity coefficient of the corresponding compensation unit based on voltage fluctuation, actual compensation current and target compensation current, update the safety factor based on the operating parameters of each compensation unit, and return to step 2.

[0011] In this invention, in step 2, the fundamental components of the current and voltage of each phase are extracted from the current and voltage signals of each phase sequence by frequency domain separation, and the fundamental current and current phase are generated based on the fundamental components of the current, and the fundamental voltage and voltage phase are generated based on the fundamental components of the voltage.

[0012] In this invention, the current power factor of each phase is calculated based on the current phase and voltage phase of each phase sequence, the current active power and current reactive power are calculated by combining the fundamental current and fundamental voltage, and the target compensation amount of each phase is calculated based on the current reactive power and the target power factor.

[0013] In this invention, in step 3, the maximum compensation amount is calculated based on the maximum power factor, and the total capacity range of each phase is determined by combining the target compensation amount and the maximum compensation amount of each phase sequence. The capacity of each compensation unit of each phase sequence is combined, and multiple sets of compensation unit combinations with a total capacity within the total capacity range are selected.

[0014] In this invention, in step 3, a corresponding investable index is generated based on the safety factor of each compensation unit in each compensation unit combination, and the compensation unit combination with the highest investable index is taken as the target compensation unit combination.

[0015] In this invention, in step 4, the fundamental components of the current and voltage after compensation for each phase are extracted from the current and voltage signals of each phase sequence, and the fundamental current and fundamental voltage after compensation are generated. The actual compensation current is calculated based on the fundamental current before and after compensation, and the voltage fluctuation relative to the zero line is calculated based on the fundamental voltage after compensation.

[0016] In this invention, in step 5, the voltage fluctuation rate is calculated based on the voltage fluctuation, the compensation efficiency is calculated based on the actual compensation current and the target compensation current, the capacity weight is calculated based on the total capacity of the target compensation unit combination, and the capacity coefficient of the corresponding compensation unit is updated by combining the voltage fluctuation rate, the compensation efficiency and the capacity weight.

[0017] In this invention, in step 5, the working parameters include the current cut-out interval, the cumulative input time, and the real-time temperature. The current cut-out interval, the cumulative input time, and the real-time temperature of each compensation unit are collected, and the safety factor of the compensation unit is updated.

[0018] A power distribution device for implementing the automatic reactive power compensation method includes:

[0019] Multiple sets of compensation units are configured to provide a fixed compensation current to the three-phase line;

[0020] The voltage acquisition unit is configured to acquire voltage signals from a three-phase line;

[0021] The current acquisition unit is configured to acquire the current signal of a three-phase line;

[0022] The data processing unit is configured to calculate the target compensation amount for each phase sequence;

[0023] The data analysis unit is configured to generate a combination of target compensation units;

[0024] The control unit is configured to generate switching commands for the compensation unit;

[0025] The data update unit is configured to update the safety factor and capacity factor of at least one set of compensation units.

[0026] In this invention, the compensation unit includes a capacitor and a switching bridge, which consists of four sets of thyristors connected in parallel to the neutral line and any phase sequence of the three-phase line.

[0027] The power distribution method and equipment for automatic reactive power compensation according to the present invention have the following beneficial effects: The present invention collects the current and voltage signals of the three-phase lines, extracts the fundamental components of the voltage and current of each phase sequence through frequency domain separation, calculates the target compensation amount of reactive power for each phase, updates the capacity value of the compensation unit through the capacity coefficient, generates multiple sets of compensation unit combinations by combining the target compensation amount and the capacity value, and then extracts the target compensation unit combination based on the safety factor of the compensation unit. This can improve the accuracy of reactive power compensation for each phase sequence and the accuracy of compensation unit deployment. Furthermore, after deploying the target compensation unit combination, the voltage and current signals of the three-phase lines are collected again, the voltage fluctuation rate and compensation efficiency of each phase sequence are calculated, and the capacity coefficient of the corresponding compensation unit is updated by combining the capacity weight. This can more accurately predict the capacity change of the compensation unit. In addition, the present invention also updates the corresponding safety factor by collecting the operating parameters of each compensation unit, thereby evaluating the reliability of the compensation unit and balancing the operating losses of each compensation unit. Attached Figure Description

[0028] Figure 1This is a flowchart of the power distribution method for automatic reactive power compensation according to the present invention;

[0029] Figure 2 This is a circuit diagram of the power distribution method for automatic reactive power compensation according to the present invention.

[0030] Figure 3 This is a preferred circuit diagram of the compensation unit of the present invention;

[0031] Figure 4 This is a schematic diagram illustrating the generation of the target compensation unit combination according to the present invention;

[0032] Figure 5 This is a waveform diagram of the actual load voltage and current before compensation.

[0033] Figure 6 This is an ideal waveform diagram of the compensated load voltage and current;

[0034] Figure 7 This is a diagram showing the mapping relationship between voltage and current in different coordinate systems according to the present invention;

[0035] Figure 8 This is a schematic diagram illustrating the detection of instantaneous fundamental current according to the present invention;

[0036] Figure 9 This is a block diagram of the power distribution equipment used in the power distribution method for implementing the automatic reactive power compensation of the present invention.

[0037] The reference numerals in the attached figure are: capacitor 10, thyristor 20. Detailed Implementation

[0038] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0039] In power grid systems, reactive power balancing and accurate compensation play a crucial role in maintaining voltage stability, reducing line losses, and improving power quality. Existing technologies typically employ fixed-capacity or grouped capacitor banks for reactive power compensation. Because the capacitor capacity is fixed, multi-stage capacitor switching systems often use the same combination of compensation units for similar reactive power, leading to repeated switching of some compensation units. This affects the overall lifespan and reliability of the system, resulting in reactive power compensation capacity drift. To address these issues, this invention proposes a power distribution method and equipment for automatic reactive power compensation. Example 1

[0040] like Figures 1 to 8As shown, the present invention provides a power distribution method for automatic reactive power compensation, comprising the following steps. This method achieves independent compensation for the three phases through a compensation unit connected to the neutral line. A safety factor characterizes the repeated switching of the compensation unit, a capacity factor characterizes the capacity change of the compensation unit, the safety factor is updated by collecting the operating parameters of the compensation unit, and the capacity factor is corrected by predicting single-phase-to-ground voltage fluctuations through the neutral line. This allows for more accurate prediction of the capacity change of the compensation unit, achieving precise compensation of reactive power in each phase.

[0041] Step 1: The distribution network is connected to multiple inductive loads via three-phase lines. Multiple compensation units of different capacities are configured between each phase sequence and the neutral line of the three-phase lines, with a preset safety factor and capacity factor for each compensation unit. For example... Figure 2 As shown, in a three-phase four-wire system, multiple inductive loads are connected. These include three-phase loads such as motors and transformers directly connected to the three-phase lines, as well as single-phase loads such as lighting circuits and household appliances connected to a specific phase sequence and the neutral line. This mixed connection method makes the power grid system prone to three-phase imbalance. To address this, multiple sets of parallel compensation units with binary proportional or arithmetic distributions of capacity are independently configured between each phase sequence (phase a, phase b, phase c) and the neutral line, forming reactive power compensation branches that can be independently switched on and off phase by phase. Figure 3 As shown, the compensation unit includes a capacitor 10 and a switching bridge, which consists of four sets of thyristors 20 connected in parallel to the neutral line and any phase sequence of the three-phase line. The initial values ​​of the safety factor and capacity factor for each compensation unit are both 1. The capacity values ​​of compensation units within the same phase sequence can be different.

[0042] Step 2: Acquire the current and voltage signals of the three-phase lines on the load side, extract the fundamental components of the current and voltage, and calculate the current power factor and target compensation amount for each phase. A preset sampling frequency is used to periodically acquire the three-phase current and voltage signals on the load side. The sampling frequency f... c It is usually set to an integer multiple of the fundamental frequency, f c =Xf1H max Where X is a multiple, typically ranging from 3 to 15. f1 is the fundamental frequency, usually 50Hz or 60Hz. H max The maximum harmonic order is used. For example, when the fundamental frequency is 50Hz and the maximum harmonic is the 50th harmonic, the sampling frequency can be set to 10kHz. In this invention, voltage and current signals for each phase sequence are acquired through voltage transformers and current transformers connected to the three-phase line.

[0043] The fundamental components of the current and voltage of each phase are extracted from the current and voltage signals of each phase sequence through frequency domain separation. A fundamental current and current phase are generated based on the fundamental current component, and a fundamental voltage and voltage phase are generated based on the fundamental voltage component. Further, the current power factor of each phase is calculated based on the current phase and voltage phase of each phase sequence. The current active power and current reactive power are calculated by combining the fundamental current and fundamental voltage. The target compensation amount for each phase is calculated based on the current reactive power and the target power factor. The calculation process for the target compensation amount is as described in Example 2.

[0044] Step 3: Update the capacity value of the compensation unit based on the capacity coefficient. Combine the capacity value and the target compensation amount of each phase to generate multiple sets of compensation unit combinations for the corresponding phase sequence. Extract the target compensation unit combination from the compensation unit combinations based on the safety factor and calculate the target compensation current. Calculate the maximum compensation amount based on the maximum power factor. Combine the target compensation amount and the maximum compensation amount of each phase sequence to determine the total capacity range of each phase, as described in Example 2. Update the capacity value C of the compensation unit based on the capacity coefficient g, and the updated capacity value C' = gC. Combine the capacities of each compensation unit in each phase sequence and select multiple sets of compensation unit combinations whose total capacity is within the total capacity range, such as... Figure 4 As shown, combinations of compensation units from the first to the Kth can be obtained. Typically, at least one set of compensation unit combinations that meets the requirements can be obtained. If there are too few spare compensation units, making it impossible to obtain a suitable compensation unit combination, the target power factor should be appropriately reduced.

[0045] Furthermore, the average safety factor of each compensation unit in each compensation unit combination is calculated and set as the operational index of the corresponding compensation unit combination. The compensation unit combination with the highest operational index is selected as the target compensation unit combination. Then, based on the total capacity Q of the target compensation unit combination for each phase sequence... x,t and fundamental current I x Calculate the target compensation current I for each phase x,t I x,t =Q x,t / I x , x∈{a,b,c}.

[0046] Step 4: After the target compensation unit combination is activated and the system stabilizes, the current and voltage signals of the three-phase lines are re-acquired. The actual compensation current of each phase and the voltage fluctuation relative to the neutral line are calculated. It should be noted that after activating the target compensation unit combination, due to switching transients and system response, it is necessary to wait 3-10 cycles for the system to stabilize before re-acquiring the current and voltage signals of the three-phase lines for at least one cycle. The fundamental components of the compensated current and voltage of each phase are extracted through frequency domain separation to generate the compensated fundamental current and fundamental voltage. Further, the actual compensation current of each phase is calculated based on the fundamental current before and after compensation for each phase sequence, and the voltage fluctuation relative to the neutral line is calculated based on the compensated fundamental voltage. Figure 5 and Figure 6 The changes in load current and voltage before and after compensation are shown. Ideally, the voltage and current after compensation are in phase.

[0047] Because harmonic currents flowing into capacitors can easily lead to harmonic amplification or even resonance, this causes a rapid increase in capacitor temperature and accelerates the aging of related components. In a more preferred embodiment, an active power filter (APF) can be used to manage harmonic currents in the power grid before the compensation unit is activated. Specifically, a power matrix can be generated by real-time acquisition of instantaneous voltage and current of the three-phase lines. Then, the DC and AC components of active and reactive power in the power matrix are separated to extract the fundamental active and reactive power. Based on the fundamental active and reactive power, the instantaneous fundamental current for each phase sequence is generated, thereby obtaining the instantaneous harmonic current for each phase. Finally, as... Figure 2 As shown, the active filter generates a corresponding harmonic current command based on the instantaneous harmonic current of each phase sequence, and injects a compensation current with the same amplitude but opposite phase as the instantaneous harmonic current into each phase line in real time, thereby effectively eliminating harmonics and improving the accuracy of reactive power compensation in subsequent compensation units. The calculation process of the instantaneous harmonic current is described in Example 5.

[0048] Step 5: Update the capacity coefficient of the corresponding compensation unit based on voltage fluctuation, actual compensation current, and target compensation current; update the safety factor based on the operating parameters of each compensation unit; and return to Step 2. The operating parameters include the current cut-off interval, cumulative commissioning time, and real-time temperature. Specifically, calculate the voltage fluctuation rate based on voltage fluctuation, calculate the compensation efficiency based on the actual compensation current and target compensation current, calculate the capacity weight based on the total capacity of the target compensation unit combination, and update the capacity coefficient of the corresponding compensation unit by combining the voltage fluctuation rate, compensation efficiency, and capacity weight, as described in Example 3.

[0049] Furthermore, the safety of the compensation unit is affected by factors such as the cut-out interval, the input time, and the temperature; some compensation units are repeatedly switched on and off due to their suitable capacity. Therefore, repeated switching should be avoided as much as possible, ensuring a sufficient time interval between two switching actions. This invention collects the current cut-out interval, the cumulative input time, and the real-time temperature of each compensation unit. It calculates the cut-out coefficient based on the current cut-out interval, the input coefficient based on the cumulative input time, and the temperature rise coefficient based on the real-time temperature, and combines these with weights to generate a safety factor for each compensation unit. In this invention, the real-time temperature of the corresponding compensation unit can be collected by a temperature sensor installed on the capacitor. The preferred method for generating the safety factor is described in Embodiment 4. Example 2

[0050] This embodiment further discloses a preferred method for calculating the target compensation amount for each phase sequence. Considering the three-phase imbalance problem in the power grid, this invention performs phase-by-phase compensation for the three-phase lines by calculating the target compensation amount for each phase sequence. Taking phase a as an example, the calculation process is as follows.

[0051] The fundamental components of voltage and current are extracted. In this embodiment, the current data of phase a is separated in the frequency domain by Fast Fourier Transform (FFT) to obtain the complex frequency domain sequences of the fundamental component and each harmonic component. The amplitude a1 and phase φ1 of the fundamental component are extracted from the complex frequency domain sequences to obtain the fundamental current I. a and current phase φ ai , φ ai= φ1. The fundamental component is extracted from the voltage data using the same method, and then the fundamental voltage U is obtained. a and voltage phase φ au .

[0052] Calculate the current reactive power and the target reactive power. Based on the voltage phase φ of phase a. au and current phase φ ai Calculate the current power factor angle φ a φ a =φ au -φ ai Thus, the current power factor cosφ is obtained. a Based on the current power factor cosφ a Calculate the current active power P of phase a. a and current reactive power Q a,s P a =U a I a cosφ a Q a,s =P a tanφ aBased on the target power factor δ, the target power factor angle φ can be obtained. t φ t =arccosδ. At this point, the target reactive power Q... a,t =P a tanφ t In this embodiment, the target power factor is 0.95. A higher target power factor is generally not always better; in temporary power distribution systems, a target power factor of 0.95 to 0.98 is typically chosen.

[0053] Calculate the target compensation amount and the maximum compensation amount. Calculate the target compensation amount Q based on the current reactive power and the target reactive power. a,c Q a,c =Q a,s -Q a,t =P a (tanφ t -tanφ a Similarly, based on the maximum power factor δ max The maximum compensation amount Q can be calculated. a,m Q a,m =P a [tan(arccosδ max )-tanφ a It should be noted that, to prevent overcompensation by the compensation unit, the maximum power factor δ... max It should be less than 1. For example, when the target power factor is 0.95, the maximum power factor can be set to 0.97. Furthermore, based on the target compensation amount Q... a,c and maximum compensation Q a,m The total capacity range [Q] can be obtained. a,c Q a,m ].

[0054] Finally, the target compensation amount and maximum compensation amount of phase b and phase c are calculated using the same method, thereby obtaining the total capacity range of the corresponding phase sequence. Example 3

[0055] This embodiment further discloses a preferred method for updating the capacity coefficient. In this invention, the capacity coefficient of the corresponding compensation unit is corrected by calculating the voltage fluctuation relative to the neutral line for each phase sequence. Taking phase a as an example, the specific process is as follows.

[0056] Calculate the voltage fluctuation rate. Based on the fundamental voltage U after phase a compensation. a 'Calculate the voltage fluctuation ΔU between this phase and the neutral line.' a0 =|U a '-U0|. U0 is the reference voltage, typically 220V in engineering applications. Voltage fluctuation rate w a =ΔU a0 / ΔU th ΔU th ΔU is the threshold for voltage fluctuation. th Typically less than 5%U0. In a more preferred embodiment, ΔU a0 / ΔU th When <1, w a =1, ΔU a0 / ΔU th When ≥1, w a =ΔU a0 / ΔU th .

[0057] Calculate the compensation efficiency. Based on the fundamental current I before and after compensation in phase a. a I a 'Calculate the actual compensation current I of phase a' a,s I a,s =I a '-I a I a,s >0. Based on the target compensation current I a,t and actual compensation current I a,s Calculate the compensation efficiency η a η a =I a,s / I a,t η a This reflects the error in the capacity coefficient of the compensation unit; the smaller the value, the greater the error. Ideally, η a =1. In this invention, the compensated fundamental current I a 'The average current value is usually taken over three to five signal cycles to avoid interference from subsequent inductive loads.'

[0058] Calculate the capacity weight. Let H be the target compensation unit combination for phase a. a ={G1,G2,…,G k ,…,G K}, where K is the number of compensation units for that phase. Based on each compensation unit G k The current capacity value C k Calculate the corresponding capacity weight μ k , k=1,2,…,K.

[0059] Update the capacity factor. Combine this with the voltage fluctuation rate w of phase a. a Compensation efficiency η a and the capacity weight μ of each compensation unit k Update the corresponding capacity factor g k The updated capacity factor g k '=λ k ·g k +(1-λk )μ k ·w a 1 / 2 ·η a ·g k Wherein, λ k For compensation unit G k The forgetting coefficient, 0 < λ k <1. The value of the forgetting coefficient can be adjusted according to the working parameters of the compensation unit. The closer its value is to 1, the slower the capacity coefficient updates. The capacity coefficient can be adjusted more smoothly through the forgetting coefficient. To reduce data fluctuations, the forgetting coefficient of each compensation unit can be set to 0.95 to 0.99 in the initial state. In a further embodiment, the capacity coefficient can also adopt the exponential forgetting algorithm, i.e., g k '=λ k ·g k +(1-λ k )μ k ·exp(w a ·η a )·g k The exponential forgetting algorithm can speed up the update of capacity coefficients, but this invention does not limit its application.

[0060] Other phase sequences can be updated with the same method to update the capacity coefficients of the compensation units introduced into that phase sequence. The accuracy of the forgetting algorithm in this embodiment is limited by the capacity coefficients. In a more preferred embodiment, in line with the spirit of this invention, a deep learning algorithm can be used to update the capacity coefficients to improve prediction accuracy. Example 4

[0061] This embodiment further discloses a preferred method for generating the safety factor of each compensation unit. Although reactive power compensation is beneficial for stabilizing the field power distribution current, repeated switching or continuous operation of a single compensation unit should be avoided as much as possible.

[0062] The current cut-out interval t of the acquisition compensation unit o Cumulative investment time t i And the real-time temperature T. The current cut-out interval refers to the time interval between the last cut-out time of the compensation unit and the current time, and the cumulative investment time refers to the sum of the time for each time the compensation unit is invested in the system.

[0063] Based on the current cut-out interval t c Calculate the cut-out coefficient S o Preset baseline switching interval t std When t c ≥t std At that time, S o =1; when 0 <t c <t std At that time, S o =tc / t std The longer the cut-out interval of the compensation unit, the larger the cut-out coefficient. The reference cut-out interval can be obtained through experimental measurement. For example, in this embodiment, t std =1h.

[0064] Based on the cumulative investment time t s Calculate the input coefficient S i S i =1-t s / t max , t max The lifespan of the compensation unit is calculated. As the cumulative operating time increases, the operating coefficient gradually decreases. Considering that high temperatures exacerbate the lifespan degradation of the compensation unit, in a more preferred embodiment, the lifespan of the compensation unit can be updated in real time using a lifespan acceleration model.

[0065] The temperature rise coefficient S is calculated based on the real-time temperature T. T S T =1-(T-T0) / (T max -T std ), T < T max Where T0 is the ambient temperature, T max T is the maximum allowable temperature of the compensation unit. std The rated ambient temperature refers to the reference ambient temperature at which the highest permissible temperature is obtained. max and T std This can be obtained from experiments or design manuals. Ideally, the temperature of the compensation unit is the same as the ambient temperature, at which point the temperature rise coefficient S... T =1. And when T≥T max At that time, S T =0. Under constant ambient temperature, the temperature rise coefficient gradually decreases as the temperature increases.

[0066] Generate a safety factor. Calculate the safety factor S based on the cut-out coefficient, input coefficient, and temperature rise coefficient, where S = ω1S o +ω2S i +ω3S T The weights of ω1, ω2, and ω3, representing the cutting coefficient, input coefficient, and temperature rise coefficient respectively, can be adjusted according to the working state of the compensation unit. Initially, ω1, ω2, and ω3 are set to 0.5, 0.3, and 0.2 respectively. The safety factor ranges from [0,1]. This invention can preset different weighting coefficients based on practical experience and on-site working conditions. The higher the safety factor of the compensation unit, the greater the likelihood of it being put into use. Example 5

[0067] like Figure 8As shown, in this embodiment, more preferably, or further, in order to improve the accuracy of reactive power compensation by the compensation unit, an active power filter (APF) is used to manage harmonic currents in the power grid before the compensation unit is activated. The calculation of instantaneous harmonic currents is as follows.

[0068] First, the instantaneous current I in the three-phase abc coordinate system is transformed using Clark transformation. an I bn I cn Mapping to the two-phase αβ stationary coordinate system, we obtain the two-phase coordinates I of the instantaneous current. α I β . The same method can be used to measure the three-phase voltage U. an U bn U cn The transformation yields the two-phase voltage U α U β .like Figure 7 As shown, in the two-phase αβ stationary coordinate system, the voltage vector e and the current vector i can be decomposed into corresponding α-axis and β-axis components U. α U β and I α I β The voltage vector e and current vector i represent the three-phase voltage U, respectively. an U bn U cn and three-phase current I an I bn I cn The vector sum of the voltage vector e and the current vector i. Furthermore, the angle θ between the voltage vector e and the current vector i in the diagram is the real-time synchronization angle provided by the phase-locked loop.

[0069] Secondly, due to the three-phase imbalance and harmonic current problems in the power grid, it is necessary to further transform the two-phase voltage and current in the two-phase αβ stationary coordinate system to the two-phase dq rotating coordinate system using the Park transformation, thereby obtaining the active and reactive components of the two-phase voltage and current. Let the active and reactive currents in the two-phase dq rotating coordinate system be I. d I q Then there is The same method can be used to obtain the active voltage U. d and reactive voltage U q At this time, the power matrix Where p is active power and q is reactive power.

[0070] Finally, the active power p and reactive power q are separated by a low-pass filter to obtain the DC component p1 and AC component p2 of the active power p, and the DC component q1 and AC component q2 of the reactive power q. p = p1 + p2, q = q1 + q2. Here, the DC components p1 and q1 correspond to the fundamental active and fundamental reactive power at the given moment, respectively. Then, through inverse coordinate transformation (inverse Park, inverse Clark), the fundamental active power p1 and fundamental reactive power q1 are restored to the instantaneous fundamental current I in the three-phase abc stationary coordinate system. sa I sb I sc This leads to the instantaneous harmonic current I of the three-phase line. ha I hb I hc I ha =I an -I sa I hb =I bn -I sb I hc =I cn -I sc . Example 6

[0071] like Figure 9 As shown, a power distribution device for implementing the automatic reactive power compensation method of the present invention includes multiple compensation units, a voltage acquisition unit, a current acquisition unit, a data processing unit, a data analysis unit, a control unit, and a data update unit. Figure 2 As shown, the first inductive load to the Mth inductive load provides reactive current and harmonic current to the three-phase line, and the compensation unit includes the first compensation unit to the Nth compensation unit.

[0072] Multiple compensation units are configured to provide a fixed compensation current to the three-phase line. For example... Figure 3 As shown, the compensation unit includes a capacitor 10 and a switching bridge, which consists of four sets of thyristors 20 connected in parallel to the neutral line and any phase sequence of the three-phase lines. When the compensation unit is put into use, under the action of the system AC voltage, the compensation unit generates and outputs a fixed capacitive current, which compensates for the reactive power of the corresponding phase. The rated capacitance of the capacitor is, for example, 165μF, 330μF, etc., and the corresponding capacity of the compensation unit is, for example, 10kVar, 30kVar, etc.

[0073] The voltage acquisition unit is configured to acquire the voltage signal of the three-phase line, which is achieved through three independent single-phase voltage transformers. Each voltage transformer is connected in parallel between the corresponding phase line and ground to complete voltage isolation and step-down transformation, and obtain the standard low voltage signal of each phase.

[0074] The current acquisition unit is configured to acquire the current signal of the three-phase line, which is achieved through three independent single-phase current transformers. Each current transformer is connected in series in the main circuit of the corresponding phase to complete the current isolation and current reduction transformation, and obtain the standard low current signal of each phase.

[0075] The data processing unit is configured to calculate the target compensation amount for each phase sequence. The unit acquires the current and voltage signals for each phase sequence via a wireless communication circuit, extracts the fundamental components of the current and voltage for each phase through frequency domain separation, generates the fundamental voltage and fundamental current, calculates the current reactive power of each phase, and calculates the corresponding target compensation amount based on the target power factor. Furthermore, the data processing unit calculates the maximum compensation amount based on the maximum power factor, and combines the target compensation amount and the maximum compensation amount to generate the total capacity range for each phase.

[0076] The data analysis unit is configured to generate target compensation unit combinations. It updates the capacity value of each compensation unit based on the capacity coefficient, generates multiple sets of compensation unit combinations based on the total capacity range of each phase sequence and the capacity values ​​of each compensation unit, extracts the target compensation unit combination based on the safety factor, and then calculates the target compensation current. In addition, the data analysis unit calculates instantaneous harmonic currents based on the instantaneous voltage and instantaneous current of the three-phase line.

[0077] The control unit is configured to generate switching commands for the compensation units. Based on the target compensation unit combination for each phase sequence, the control unit generates the corresponding switching commands for the compensation units to control their activation or deactivation. The control unit can also generate harmonic compensation commands for each phase based on the instantaneous harmonic current of each phase sequence to control the active filter to output the corresponding harmonic compensation current. The control unit is, for example, an SVG controller.

[0078] The data update unit is configured to update the safety factor and capacity factor of at least one set of compensation units. The data update unit updates the safety factor of each compensation unit based on the real-time temperature, current cut-off interval, and cumulative input time, and updates the capacity factor of each compensation unit based on compensation efficiency, voltage fluctuation rate, and forgetting factor.

[0079] Furthermore, the power distribution equipment of the present invention may also include a sensing unit, a clock unit, an active filter, a storage unit, a display unit, and communication lines. The sensing unit records the real-time temperature of each compensation unit, which is achieved through temperature sensors installed on each capacitor. Figure 2As shown, the sensing unit includes a first sensing unit to an Nth sensing unit. The clock unit records the time parameters of each compensation unit, including the activation and deactivation times. The storage unit stores the target compensation unit combination for each phase sequence. The active filter provides harmonic compensation current. The display unit displays grid status information, including but not limited to the reactive power and power factor of the three phases, and the activation status of the compensation units. The communication lines include wireless and wired communication lines. The wireless communication line connects the acquisition unit, data analysis unit, and data processing unit, while the wired communication line connects the data analysis unit and the display unit. The communication lines enable remote control, preventing power signals from affecting the operation of this invention.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A power distribution method for automatic reactive power compensation, characterized in that, Includes the following steps: Step 1: The distribution network is connected to multiple inductive loads via three-phase lines. Multiple compensation units with different capacities are configured between each phase sequence and the neutral line of the three-phase lines. The safety factor and capacity factor of each compensation unit are preset. Step 2: Collect the current and voltage signals of the three-phase line on the load side, extract the fundamental components of the current and voltage, and calculate the current power factor and target compensation amount of each phase. Step 3: Update the capacity value of the compensation unit based on the capacity coefficient, generate multiple sets of compensation unit combinations corresponding to the phase sequence by combining the capacity value and the target compensation amount of each phase, extract the target compensation unit combination from the compensation unit combination based on the safety factor, and calculate the target compensation current; Step 4: Activate the target compensation unit combination. After the system stabilizes, re-acquire the current and voltage signals of the three-phase lines, and calculate the actual compensation current of each phase and the voltage fluctuation relative to the neutral line. Step 5: Update the capacity factor of the corresponding compensation unit based on voltage fluctuation, actual compensation current, and target compensation current; update the safety factor based on the operating parameters of each compensation unit; return to Step 2. In step 5, the voltage fluctuation rate is calculated based on the voltage fluctuation, the compensation efficiency is calculated based on the actual compensation current and the target compensation current, the capacity weight is calculated based on the total capacity of the target compensation unit combination, and the capacity coefficient of the corresponding compensation unit is updated by combining the voltage fluctuation rate, compensation efficiency, and capacity weight. The operating parameters include the current cut-out interval, cumulative deployment time, and real-time temperature. The current cut-out interval, cumulative deployment time, and real-time temperature of each compensation unit are collected, and the safety factor of the compensation unit is updated. The cut-out coefficient is calculated based on the current cut-out interval, the input coefficient is calculated based on the cumulative input time, the temperature rise coefficient is calculated based on the real-time temperature, and the safety factor is calculated based on the cut-out coefficient, the input coefficient, and the temperature rise coefficient.

2. The power distribution method for automatic reactive power compensation according to claim 1, characterized in that, In step 2, the fundamental components of the current and voltage of each phase sequence are extracted from the current and voltage signals of each phase sequence by frequency domain separation. The fundamental current and current phase are generated based on the fundamental current components, and the fundamental voltage and voltage phase are generated based on the fundamental voltage components.

3. The power distribution method for automatic reactive power compensation according to claim 2, characterized in that, The current power factor of each phase is calculated based on the current phase and voltage phase of each phase sequence. The current active power and current reactive power are calculated by combining the fundamental current and fundamental voltage. The target compensation amount of each phase is calculated based on the current reactive power and the target power factor.

4. The power distribution method for automatic reactive power compensation according to claim 1, characterized in that, In step 3, the maximum compensation amount is calculated based on the maximum power factor. The total capacity range of each phase is determined by combining the target compensation amount and the maximum compensation amount of each phase sequence. The capacity of each compensation unit in each phase sequence is combined, and multiple sets of compensation unit combinations with a total capacity within the total capacity range are selected.

5. The power distribution method for automatic reactive power compensation according to claim 1, characterized in that, In step 3, a corresponding investable index is generated based on the safety factor of each compensation unit in each compensation unit combination, and the compensation unit combination with the highest investable index is taken as the target compensation unit combination.

6. The power distribution method for automatic reactive power compensation according to claim 1, characterized in that, In step 4, the fundamental components of the current and voltage after compensation for each phase are extracted from the current and voltage signals of each phase sequence to generate the fundamental current and fundamental voltage after compensation. The actual compensation current is calculated based on the fundamental current before and after compensation, and the voltage fluctuation relative to the neutral line is calculated based on the fundamental voltage after compensation.

7. A power distribution device for implementing the automatic reactive power compensation method of claim 1, characterized in that, include: Multiple sets of compensation units are configured to provide a fixed compensation current to the three-phase line; The voltage acquisition unit is configured to acquire voltage signals from a three-phase line; The current acquisition unit is configured to acquire the current signal of a three-phase line; The data processing unit is configured to calculate the target compensation amount for each phase sequence; The data analysis unit is configured to generate a combination of target compensation units; The control unit is configured to generate switching commands for the compensation unit; The data update unit is configured to update the safety factor and capacity factor of at least one set of compensation units.

8. The power distribution equipment according to claim 7, characterized in that, The compensation unit includes a capacitor and a switching bridge, which consists of four sets of thyristors connected in parallel to the neutral line and any phase sequence of the three-phase lines.

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